Figure 1.

Baboon APOL1 is less pH-dependent than human APOL1. A, schematic of the planar lipid bilayer system. B, a bilayer was formed in symmetric solutions of chamber buffer, pH 7.2 (see “Materials and methods”). The current was recorded (top trace, pA) as the voltage was manipulated (bottom trace, mV). 180 ng of HsAPOL1 was added to the cis solution, which was then acidified to pH 6.6 with HCl, before being reneutralized with KOH (pH 7.2). During this period, no change in current occurred (except for a brief aberration indicated with an asterisk). In contrast, PhAPOL1 addition to the cis side of the same bilayer resulted in a gradual conductance increase at pH 7.2 (5-pA scale, left of dashed line) and a faster rate of increase when the cis side was adjusted to pH 6.6 (250-pA scale, right of dashed line).